1. Field of the Invention
The present invention relates generally to a fastening system for securing apertured members together in a secure and sealed condition by means of a sealing capped nut and a bolt therefor to receive a portion of a formable hollow shank on the capped nut for formation of a seal under the bolt head. More particularly, the present disclosure relates to an improved method for the fastening of apertured members made of fiberglass-reinforced polyester/plywood laminates to the structural members for transportation equipment, such as intermodal cargo containers and truck trailers for over-the-highway use by means of the use of a sealing capped nut having a formable hollow shank thereon to sealingly engage the bolt and the apertured members in secured engagement.
2. Description of the Prior Art
All metal intermodal cargo containers and truck trailers such as the all aluminum example thereof have been utilized in industry for a long period of time. The cost of these containers and trailers has risen substantially, due to the cost of the raw materials and the methods of manufacturing the finished product such that fiberglass-reinforced polyester/plywood is now being used to reduce costs and is experiencing rapid growth for the construction of such containers due to the lesser cost and improved characteristics such as structural integrity and aesthetic appearance. The use of these materials began some time in the late 1960's and early 1970's by truck trailer manufacturers who were experimenting with the material which today has achieved approximately 9-14% penetration of the marketplace for the use of such materials in truck trailers and truck bodies. These FRP/plywood materials generally consist of a layer of plywood sandwiched between two layers of reinforced plastic material. The plastic material can be of any polymeric substance, but most often has been of the polyester type being reinforced with glass fibers. The plastic is bonded by heat and pressure to the plywood core and the composite material combines the flexibility of plywood with the stiffness of fiberglass-reinforced plastic to provide a material which is lightweight and durable. This allows for the use of fewer structural members while providing good design aerodynamics and aesthetically pleasing exterior surface. Perhaps chief among the advantages of such material is the ease of repair of any damaged areas and its resistance to puncture.
The method of construction of containers and trailers of these materials is similar to that utilized in the construction of all metal containers or trailers. The problem with such FRP/plywood panels is that with apertures being drilled therethrough for the fastening of these panels to steel frames as in cargo containers or the extruded aluminum frames as in truck trailers, the exposure of the plywood core to the environment can cause problems with adhesive strength of the materials which have been laminated and with swelling and general deterioration of the plywood core. The typical 20' containers, for instance, require approximately 400 fasteners, while a typical 44' trailer requires generally about 600 fasteners to fasten the panels to the structural members. A mastic sealant is usually brushed on between the panels and the frame to help in sealing out moisture.
The requirement for a fastening system to achieve the fastening of these panels to their structural members are unusual, since the plastic overcoats are brittle in nature, while the core of plywood is highly compressible, causing problems if the fasteners are overloaded, and yet the fasteners must be loaded sufficiently to properly fasten the panels to their structural members. Furthermore, it is highly desirable to have the nut heads and bolt heads display a low profile on the exterior portions thereof to avoid hitting them in the use of these containers or trailers and to maximize the usable interior width and height of the container or trailer. In the past, several fastening systems have been utilized which are of the nut and bolt type to generally fill the apertures drilled therethrough to provide a sealing engagement to obtain a moisture-free internal bore on the materials.
One commonly used fastening system in this industry for fastening apertured panels of the FRP/plywood to the structural members for the production of cargo containers or tractor trailers consists of a sleeve which is inserted completely through the bore of the panels and the structural members which is inserted from the plywood side having a flange head which fits flushly over the plywood surface. Thereafter, a pin is inserted through the opposite side of the sleeve and subsequently an installation tool is applied to the pin tail and actuated to pull the pin into contact with the joint member and causing the sleeve end to curl and lock into the formed pin head, such as the action of a blind or pop rivet utilized for the connection of metallic panels. The installation tool thereafter breaks the pin in tension with a break point groove substantially flush with the head of the sleeve so that there is no projecting pin left to be cut off in a separate operation.
Another type of fastening system employs a bolt member generally having a gripping material on the threads adapted for engagement with a specially constructed tapped through nut member to achieve the desired clamping action between the frame and the panel sections. The bolt member includes an anti-rotation means which also achieves a centering of the threaded portion of the bolt relative to the panel apertures and is provided with a sealing element under the head. The nut member is engaged from the other side which has a drive means and a tapped through hole. Upon clamping engagement with the bolt, the sealing element provides protection against entry of moisture into the threaded portion of the assembly.
The first system mentioned above includes a significant disadvantage in terms of waste material consisting of the throw-away shank which is snapped off from the installed fastener. Furthermore, with this rather open flush mount side, moisture can enter into the cracks between the bolt and the sleeve member, promoting oxidation of the fastener, which can cause loosening of the fastener. This allows moisture to seep into the core of the aperture bore, resulting in swelling or deterioration of the plywood core. Furthermore, there is an inability to adjust or replace these fasteners conveniently.
A major problem and disadvantage of the second system mentioned above is the weight when up to 600 of these fasteners are used on each unit of production. Furthermore, by using a sealing collar on the bolt member of these fastener systems, there is no assurance of the integrity of the seal through the entire bore diameter of the apertures, thus causing a possible leak in the moistureproofing of these bore diameters. Furthermore, since these components are all metallic in nature, given the fact that different metallic materials are used with regard to the frame members for the structural support of the panels, electrolytic actions result, causing rapid oxidation of one of the members of the fastening system or the frames of the containers. This is highly undesirable aesthetically and could mean replacement of these members sooner than the wear life of the panels and the frame structures. The replacement of corroded components is difficult.
A further disadvantage of the second system is the cost of manufacture, since separate operations are required to manufacture the sealing element, the bolt, the nut, the installation of the sealing element on the bolt, and the thread gripping media on the bolt. Because it is hard to control the exact amount of thread gripping media, the torque-to-tension relationship can vary. When loosening of the fastener damages the thread gripping media, the torque-to-clamp force relationship can be destroyed.
Therefore, it would be exceedingly advantageous in terms of reducing manufacturing costs, maintenance problems, weight and providing extended life to the use of panels for the construction of cargo containers and tractor trailers to have a fastening system which will effectively seal, fasten, and solve the problems attendant to the use of such fastening devices for the fastening situation as hereinabove described.